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Centre for Evidence-
Based Medicine

Example NNTs - Opthalmology

Condition or Disorder Intervention vs. Control Outcome Follow-up Duration Event Rates % NNT (95% CI)
CER EER
Second-eye cataract surgery1 Surgery vs. control Difficulty reading normal print 6 months 35 6 4 (3 to 6)
Eyesight prevented most activities 11 0 10 (6 to 23)
Below-average overall vision 18 0 6 (4 to 10)
Eyesight interfered greatly in life 26 1 5 (3 to 7)
Stereoacuity worse than 3000-sec arc 70 12 2 (2 to 3)

References

  1. Lancet 1998 Sep 19;352(9132):925-9

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